1 INTRODUCTION

Paper expands when it is moistened and contracts when it is dry. Because of its absorbency, or hygroscopic nature, paper is dimensionally unstable when exposed to varying degrees of moisture. Depending on the length of fibres, their orientation, the degree of hydration, or the thickness and density of the sheet, paper may expand and contract drastically or little, unevenly or uniformly, when its moisture content changes.

These characteristics, so eloquently described by Keyes (1978, 5), are especially significant when considering the treatment of chine coll� prints. A chine coll� print consists of two sheets of paper: one thin image-bearing paper called the chine, and one thicker support paper, the plate paper. The sheets are adhered to each other when damp, during the printing process. The difference in the nature of the two sheets (thickness, density, fiber content, surface texture, moisture sensitivity, etc.) and the interplay of these differences create artistic qualities that cannot be achieved by any other printing technique. Equally, if the sheets become separated over time, or in the course of conservation treatment, these differences can work against the successful reunion of the chine coll� parts. The challenge for the conservator, when faced with objects that have unusual or competing characteristics, is to find ways to look beyond conventional approaches, to find solutions that work.

This paper discusses the treatment of a chine coll� lithograph by Odilon Redon, L'Art Celeste (1894), from the collections of the Fine Arts Museums of San Francisco.